This chapter examines the evolution of legal systems and reviews some of the principal classical and contemporary theories of law and society. It differentiates between traditional, transitional, and modern legal systems. The chapter describes how Baron de Montesquieu, Herbert Spencer, and Sir Henry Sumner Maine conceptualized the relationship between legal change and social change. It also describes how the critical legal studies (CLS) movement, feminist legal theory, critical race theory and the law and literature/rhetoric movement have challenged earlier understandings of law and society. The chapter then discusses legal evolution with respect to three types of legal systems: traditional legal systems, transitional legal systems, and modern legal systems. It then explores the influential theoretical explanations of law and society of Karl Marx, Max Weber, and Emile Durkheim. CLS is a controversial addition to the ongoing jurisprudential debate on law, legal education, and the role of lawyers in society.